Uninterruptible power supplies (UPS's) have long been used to provide at least temporary auxiliary power to electronic devices. Typically, a UPS is configured to switch between a primary power source and a standby power source as necessary to maintain constant power to a load.
For example, the primary power source may be a utility power supply, and the standby power source may take the form of a battery system. The UPS will normally operate in a line mode in which the utility power signal is passed to the load when the utility power signal is within predefined parameters. In the line mode, the UPS will typically also charge the battery system. When the utility power falls outside of the predefined parameters, the UPS will switch to standby mode in which an AC signal is generated based on the energy stored in the battery system.
A class of UPS's employs a ferroresonant transformer. A ferroresonant transformer is a saturating transformer that employs a tank circuit comprised of a resonant winding and capacitor to produce a nearly constant average output even if the input to the transformer varies. A typical UPS employing a ferroresonant transformer takes advantage of the voltage regulating properties of a ferroresonant transformer in both line and standby modes. In the context of a UPS, a ferroresonant transformer thus provides surge suppression, isolation, short circuit protection, and voltage regulation without the use of active components.
Conventionally, a ferroresonant transformer configured for use in a UPS system includes a core and an inductor arranged relative to the core to define: (a) a primary or input side of the transformer and (b) a secondary or output side of the transformer. A conventional ferroresonant transformer used in a UPS will further comprise input windings and inverter (resonant) windings arranged on the primary or input side and output windings on the secondary or output side.
An object of the present invention is to provide improved ferroresonant transformers for use in UPS systems.